Optical recording medium, method of producing the same and method of producing the optical recording card

ABSTRACT

An optical recording medium includes a silver grain layer containing a large number of blackened fine silver grains and a coloring matter layer containing coloring matter on a base board and the coloring matter has an ability of absorbing near-infrared ray. When laser beam having a density of optical energy more than a boundary which represents a threshold with respect to the density of optical energy is radiated to the optical recording medium, a part of the latter is deformed to form a plurality of convexities which will be utilized as optical recording pit. The recording pits formed in this way are detected by presence or absence of reflection of radiated light whereby the content of optical recorded informations can be read. The optical recording pits are not deformed further irrespective of how long a reading light comprising laser beam having a density of energy less than the threshold is repeatedly radiated to the optical pits. Accordingly, any reduction of S/N ratio of a signal does not take place as time elapses.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical recording medium, a methodof producing the same and a method of producing an optical recordingcard, and more particularly to a writable type (DRAW type) opticalrecording medium, a method of producing the same and a method ofproducing an optical recording card.

The optical recording medium is used when sound, image and other type ofsignal are recorded optically, and it is utilized in the form of a discor card. In the recent years, a card in which various kinds ofinformations are recorded are widely put in practical use as ID card,cash card or bank card.

2. Prior Art

A disc having an optical recording medium incorporated therein is widelyused as a recording member in which digital signals relative to soundand image are recorded. This kind of card is required to record variouskinds of informations such as individual data, data concerning anissuance company or the like. In the eariler age, such kinds ofinformations were recorded using visual characters and symbols and inthe later age they are recorded using electrical signals which areproduced with the aid of magnetism. However, in a case where magnetismrecording medium is used, recorded informations are easy to befalsified. Accordingly, there is a need of taking adequate actions forpreventing recorded informations from being falsified and moreoverdealing with the current increased quantity of informations to berecorded.

To this end, an optical recording card to which laser technique isapplied has been lately developed. This optical recording card is suchthat it is provided with an information recording medium which has anoptical reflection surface. Lately, a writable type (DRAW type)information recording medium has been required in addition to aconventional read only memory type (ROM type) recording medium.

As shown in FIG. 7, a conventional DRAW type optical recording card 101is so constructed that a gelatine layer 103 with silver gains serving asoptical recording medium is formed on a transparent card front board102, a transparent film 105 having printed patterns 104 formed thereonis adhesively secured to the bottom surface of the gelatine layer 103with silver grains with the use of a transparent adhesive 106 and a cardrear board 107 is adhesively secured to the bottom surface of thetransparent film 105 as viewed in the drawing with the use of atransparent adhesive 108.

A laser beam for the purpose of writing is introduced from a card frontboard 102 side to melt the gelatine layer 103 with silver grains,causing the non-reflective layer to be exposed to the outside, whereby apit is formed in which informations are recorded. Reading of therecorded informations is achieved by discriminating "0" from "1" independence on an intensity ratio of reflected lights from the pit andthe gelatine layer 103 with silver grains.

A structure of the DRAW type optical recording medium and a method ofproducing the same are disclosed, for instance, in an official gazetteof Japanase Patent Publication NO. 23716/1984. However, in theconventional optical recording medium, silver halide emulsion is usedfor forming the gelatine layer 103 with silver grains and formation ofthe latter requires strict control relative to developing conditions andmany complicated steps of exposing and developing, resulting in it beingproduced at an expensive cost. Further, the conventional opticalrecording medium is such that the recording portion is circularlyrecessed under the effect of energy of laser beam and the non-reflectivelayer is exposed to the outside to build a recording part. In theconventional optical recording medium, an intensity of reading light isweak in the range of 1/5 to 1/10 of that of recording light but thenon-recording portion is brought in a state close to the recordingportion under the influence of accumulative energy with the result thata ratio of S/N is reduced and preservability of recorded informations isdegraded. As another optical recording medium, there are known thosethat utilize metallic brightness of cyanine dyestuff film andabsorbability of laser beam and those that are so constructed that PVAor gelatine layer serving as a photosensibility increasing layer issuperposed on the cyanin dyestuff film in a contacted state. In thesecases, in order to effect preformatting, patterning of the dyestuff filmor patterning of the reflection amplifying film is required, resultingin a process of production becoming complicated. Also in these cases,the above-mentioned materials are used as recording material byutilizing their thermal deformation, fading, decomposition or the likebut reduction of S/N is brought about as weak reading light isrepeatedly radiated by many times. Consequently, reservability ofrecorded informations is degraded.

Accordingly, it is preferable that an optical recording medium is notmaterial which continuously varies relative to beam power but it ismaterial with which presence and absence of recorded informations isrecognized in the presence of a certain "threshold".

DISCLOSURE OF THE INVENTION

The present invention has been made with the foregoing background inmind and its object resides in providing an optical recording mediumwhich has an excellent reservablity of recorded informations and is easyto be produced and with which preformatting is easily effected, a methodof producing the aforesaid optical recording medum and a method ofproducing an optical recording card with the use of the opticalrecording medium.

To accomplish the above object, there is provided according to a firstaspect of the invention an optical recording medium, wherein a baseboard, a silver grain layer containing a large number of fine silvergrains therein, the silver grain layer being located on the base board,and a coloring matte layer containing coloring matter which has anability of absorbing near-infrared ray, the coloring matter layer beinglocated on the silver grain layer, are superposed one above another tobuild a layered structure.

Further, there is provided according to a second aspect of the inventiona method of producing an optical medium, wherein the method comprisesthe steps of forming a silver grain layer containing silver grains,blackening a photosensitive member comprising silver grain layer byallowing the photosensitive member to be exposed to light, developed andfixed and forming coloring matter layer containing a coloring matterwhich has an ability of absorbing nea-infrared ray, the coloring matterlayer being located on the silver grain layer.

Further there is provided according to a third aspect of the invention amethod of producing an optical recording card, wherein the methodcomprises the steps of temporarily adhering to a transparent card frontboard an optical recording medium including a silver grain layercontaining a large number of fine silver grains and a coloring matterlayer containing coloring matter which has an ability of absorbingnear-infrared ray on a base board to build a layered structure in such amanner that the coloring matter layer faces the card front base board,adhering a first intermediate layer to the coloring matter layer side ofthe card front board, adhering a second intermediate layer to the firstintermediate layer and adhering a card rear board to the secondintermediate layer.

When laser beam is radiated to the optical recording medium from thecoloring matter layer side, both the silver grain layer and the coloringmatter layer located at a radiated part are deformed to a convexconfiguration to build an information pit, provided that a density ofradiated energy is higher than a predetermined threshold. Thus, it ispossible to carry out optical recording. Next, when optically recordedinformations are read, laser beam having a density of energy less thanthe threshold is radiated from the coloring matter layer side and theconvex type information pit is detected in dependence on presence andabsence of reflected light. Thus, the content of optically recordedinformations can be read.

Further, an optical recording card can be easily produced in such amanner that the optical recording medium as described above isinterposed between the card front board and the card rear board both ofwhich are adhered to one another.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmental enlarged vertical sectional view of an opticalrecording medium.

FIG. 2 is a fragmental enlarged vertical sectional view of the opticalrecording medium in FIG. 1, particularly illustrating deformationthereof.

FIGS. 3(a) to (d) illustrate the steps of producing the opticalrecording medium.

FIG. 4 is a fragmental enlarged vertical sectional view of an opticalrecording card.

FIG. 5 illustrates the steps of producing the optical recording card inFIG. 4.

FIGS. 6 (a) to (c) illustrate a test specimen used for an experimentrespectively.

FIG. 7 is a fragmental enlarged vertical sectional view of aconventional optical recording card.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, the present invention will be described in a greater detailhereunder with reference to the accompanying drawings which illustrate apreferred embodiment thereof.

In FIG. 1 reference numeral 1 designate an optical recording medium. Theoptical recording medium 1 includes a silver grain layer 3 and acoloring matter layer 4 both of which are placed on a base film 2 in alayered structure.

The silver grain layer 3 contains silver halide which is to be blackenedwhen they are exposed to light beam, developed and fixed. The silvergrain layer 3 is constituted by a coated film comprising driedphotographic emulsion. The photographic emulsion is such that granularsilver halide (silver bromide or silver chloride) is dispersed inliquidity gelatine in the form of suspension. An example of afundamental process for preparing photographic emulsion will be notedbelow.

    ______________________________________                                        first solution:                                                                           ammonium bromide 1N solution                                                                       10    cc                                                 potassium iodide 1N solution                                                                       0.5   cc                                                 gelatine             6     g                                                  distilled water      40    cc                                     second solution:                                                                          silver nitrate 1N solution                                                                         10    cc                                     ______________________________________                                    

Both the first and second solutions are maintained at a temperature of50° C. and the second solution is added to the first solusion. In thisway a required silver halide emulsion is obtained and when it is kept ata temperature of 50° C. for a period of one hour, it follows that silverbromide grains grow. The emulsion becomes solidified after it is keptunchanged for a period of full one day, and it is then subjected tocutting and water washing. Thereafter, it is heated again at atemperature of 50° C. for a period of suitable hours so as to increaseits sensivility, and it is coated and dried on the base film 2 whilehaving a film thickness of 4 microns. For instance, a polyester filmhaving a thickness of 0.1 mm is employed for the base film 2. Aphotographic film can be utilized as a combination of the base film 2and the silver grain layer 3.

A role or function of the silver grain layer 3 is to promote deformationof the coloring matter layer 4 due to the fact that if the coloringmatter layer 4 is constituted merely by a single layer, it is lessdeformed when it is exposed to laser beam for the purpose of recordingand writing. In contrast with a transparent silver grain layer 3, adarkened silver grain layer 3 absorbs light which permeates through afilm of dyestuff, improved sensivility is assured. The silver grainlayer 3 has a thickness in the range of 0.05 to 100 microns andpreferably it has a thickness in the range of 0.1 to 10 microns.

Next, description will be made below as to the coloring matter layer 4.

A role or function of the coloring matter layer 4 is to absorb andreflect of light. As a function of absorbing light, the coloring matterlayer 4 absorbs writing means (laser beam or the like) at a highefficiency whereby a writing sensibility is improved. On the other hand,as a function of reflecting light, the coloring matter layer 4 suitablyreflects reading light and writing light and thereby automatic focussingand reading of written pits can be conducted. The coloring matter layer4 has an ability of selectively absorbing near-infrared ray as anecessary nature and moreover it is required that it has a suitablereflectivity. As a dyestuff satisfying such a nature of the coloringmatter layer as mentioned above, cyanin based, phthalocyanin based,methyn based, merrocyanin based, aluminum based coloring matterbisphenildithiol Ni complex or the like will be noted here. In a case of830 nm, IR-820 (produced by Nippon Kayaku Co., Ltd.), NK-125, NK-2014,NK-2865 (each of them being produced by Nippon Kanko-Shikiso KenkyushoCo., Ltd), PA-1005, PA-1006 (each of them being produced by MitsuiToatsu Chemicals, Inc.) or the like are employable, and in a case of 780nm, NK-125 (produced by Nippon Kanko-Shikiso Kenkyusho Co., Ltd.), CY-2,CY-9(each of them being produced by Nippon Kayaku Co., Ltd) or the likeare employed. Moreover, their mixture is also effectively employable.

Formation of the coloring matter layer is carried out by spin coating,roll coating, dip coating, gravure coating, silk screen printing or thelike process, provided that a dyestuff employed therefor has anexcellent dissolubility. However, when it has less dissolubility, vacuumdepositing or the like process may be utilized.

With respect to a film thickness of the coloring matter layer, thelatter has a thickness in the range of 50 to 2000 angstroms, when thefilm is constituted by dyestuff only. And, it should be noted that resinmay be added to dyestuff. In this case, a compounding ratio of resin inthe coloring matter layer is represented by 0 to 90% by weight,preferably 0 to 70% by weight and it is suitable that it has a thicknessin the range of 100 angstroms to 1.0 micron.

Resin employable for the coloring matter layer is selected from avariety of self-oxidative resins and thermoplastic resins such asnitrocellose based resin, acrylic resin, polyester based resin,polyvinyl chloride based resin, polyvinyl acetate based resin,polystylene based resin, polyvinylbutyral based resin or the like.

It has been found from results of experiments conducted that the opticalrecording medium as constructed in the above-described manner has thefollowing nature. Namely, it has been found that a radiated part variesin shape in dependence of an amount of radiated energy, whensemiconductor laser is radiated from the coloring matter layer 3 side tothe optical recording medium 1 of which silver grain layer 3 has beensubjected to exposure and development and becomes blackened. The shapeof the radiated part varies in such a manner that it exhibits concavityas represented by reference characters B and C in FIG. 2 when a densityof radiated energy is less than the boundary and it exhibits convexityas represented by reference character A in FIG. 2 when a density ofradiated energy is higher than the boundary, wherein the boundary isidentified by 3 to 4 mW/5 μmφ (half-amplitude level). An occurrence ofvariation of shape to convexity requires temporary high energy butvariation to convexity does not take place irrespective of how manytimes laser having a lower energy is radiated thereto.

On the other hand, in a case where the silver grain layer 3 is notblackened, it follows that the radiated part becomes concave asrepresented by reference character C in FIG. 2. However, if deformationto convex configuration takes place, the convex configuration can beutilized as optical recording means by detecting it with the use ofreading light.

As will be apparent from the above description, the optical recordingmedium of the invention is merely such that a silver grain layer and acoloring matter layer are formed on the base film and a combination ofthe base film and the silver grain layer can be obtained by utilizing acommercial photographic film. Therefore, it can be very easily produced.

Since the convexly deformed portion on the radiated part is developed asshown by refrence character A in FIG. 2 only at the time when laserlight having a density of energy higher than a predetermined level isradiated temporarily, it follows that energy is only accummulated in theconvexly deformed portion without any occurrence of further deformationof the convexly deformed portion irrespective of how repeatedly readinglight having a lower density of energy is radiated thereto. Accordingly,there do not occur gradual reduction of reading accuracy and reductionof a ratio of S/N.

EXAMPLE OF EXPERIMENT

As shown in FIG. 6, the photographic emulsion was coated on a base boardG made of glass by spin coating and it was then dried. Thereafter,masking was effected from the base board side and the coated base boardwas subjected to exposing, developing and fixing in such a manner thatone half of the gelatine layer X was blackened to form a blackened partand other half of the same Y was not subjected to exposing to form atranaparent part. Next, dyestuff solusion was coated from the above ofthe gelatine layer (under conditions of 20 mg/cc, 1000 rpm and 40 sec.)to constitute a coloring matter layer whereby a test specimen wasprepared (see FIG. 6(a)). By repeating the above operations, four kindsof test specimens (test specimen 1, test specimen 2, test specimen 4 andtest specimen 4) were prepared. Laser was radiated from the above of thecoloring matter layer of each of the four kinds of test specimens toscan both the blackened part and the transparent part. As a result, aconvex configuration as shown in FIG. 6(c) was formed on the coloringmatter layer in the blackened part, while a concave groove as shown inFIG. 6(b) was formed on the coloring matter layer in the transparentpart. Results of the experiments are shown in the following table.

It was found that traces were formed by radiation of laser and theycould be utilized as a pit for the purpose of optical recording.

Recording Conditions

    ______________________________________                                        Wavelength of semiconductor laser                                                                     830 (nm)                                              diameter of spot (half-amplitude level)                                                                5 (μmφ)                                       scanning speed           5 (mm/sec)                                           ______________________________________                                    

Results of Experiments

    ______________________________________                                        Results of experiments                                                               test    test      test      test                                              specimen 1                                                                            specimen 2                                                                              specimen 3                                                                              specimen 4                                 ______________________________________                                        energy of                                                                              1.5       3.0       5.5     8.3                                      radiation                                                                     (mW)                                                                          width W of                                                                             15.00     20.00     28.00   33.00                                    convexity in                                                                  darkened part                                                                 (μm)                                                                       height h of                                                                            -0.20     -0.20     +0.05   +1.50                                    convexity in                                                                  darkened part                                                                 (μm)                                                                       width W of                                                                              9.00     11.00     15.00   17.00                                    groove in                                                                     transparent                                                                   part (μm)                                                                  height h of                                                                            -0.02     -0.07     -0.100  -0.13                                    groove in                                                                     transparent                                                                   part (μm)                                                                  ______________________________________                                    

Next, a solution comprising cyclohexanone-1.2-dichloroethane (1:1 weightratio) with IR-820+IRG-300 (1:1 weight ratio) dispersed therein at arate of 20 mg/cc was coated on HRP (high resolution plate) by spincoating under conditions of 1000 rpm and 30 sec. to form a dyestufffilm. Writablity and reflectivity at 830 nm for the test specimens areshown in the following table. As is apparent from a comparision betweenthe test speciment 2) and the test specimen 4), it is found that linedrawing (writing for optical recording) can be clearly carried out inthe presence of the coloring matter layer and the latter was veryadvantageous for writing in the form of optical recording.

Recoding Conditions

    ______________________________________                                        Recoding conditions                                                           ______________________________________                                        wavelength of semiconductor laser                                                                     830 (nm)                                              diameter of spot (half-amplitude level)                                                                5 (μmφ)                                       scanning speed           5 (mm/sec)                                           film thickness of transparent part                                                                     4.2 microns                                          silver grain layer darkened part                                                                       5.0 microns                                          ______________________________________                                        writing power                dye/   dye/                                      (mW)      black.sup.1)                                                                          transparent.sup.2)                                                                       black.sup.3)                                                                         transparent.sup.4)                        ______________________________________                                        8.2       ◯                                                                         X          ◯                                                                        ◯                             5.0       ◯                                                                         X          ◯                                                                        ◯                             3.0       ◯                                                                         X          ◯                                                                        ◯                             1.5       ◯                                                                         X          ◯                                                                        ◯                             0.5       ◯                                                                         X          ◯                                                                        Δ                                   reflectivity                                                                            4       4          18     19                                        (%) at 830 nm                                                                 ______________________________________                                         .sup.1) blackened silver grain layer on HRP which was subjected to            exposing, developing and fixing                                               .sup.2) transparent silver grain layer on HRP which was subjected to          exposing, developing and fixing                                               .sup.3) surface of the test specimen 1) with the dyestuff film formed         thereon                                                                       .sup.4) surface of the test specimen 2) with the dyestuff film formed         thereon                                                                       Evaluation                                                                    ◯: Line drawing could be conducted.                               Δ: A trace remaind.                                                      X: No variation took place.                                             

DESCRIPTION ON METHOD OF PRODUCING AN OPTICAL RECORDING MEDIUM Structure

Production of the optical recording medium 1 as described above will becarried out in the following manner.

First, as shown in FIG. 3, a silver grain layer 3 is formed on a basefilm 2 having a thickness of 0.1 mm whereby a lith film is prepared (seeFIG. 3(a)).

Next, in order that a preformat portion 6 and a optical recordingportion 8 both of which are usable for optical recording are blackenedusing a mask 5, they are subjected to exposing and they are thendeveloped and fixed (The preformat portion 6 and the optical recordingportion 8 after completion of developing and fixing are as shown by avertical sectional view of FIG. 3 (b) and a plan view of FIG. 3(c)).

Next, a dyestuff solution is coated on the blackened silver grain layer3 by roll coating and it is then dried to build a coloring matter layer4 (see FIG. 3(d)).

Now, production of the optical recording member is completed.

As dyestuff solution, a 1% anone solution which is obtained by dilutinga mixture liquid comprising IR-820 and IRG-003 by a ratio of 2:1 can beused.

Advantageous Effect

When the above-described method of producing an optical recording mediumis employed, a hitherto established photographic technique having anexcellent reliability can be utilized as it is. Thus, a required opticalrecording medium can be easily produced, while maintaing a high quality.

DESCRIPTION ON A METHOD OF PRODUCING AN OPTICAL RECORDING CARD Structure

First, the optical recording medium 1 as constructed in theabove-described manner is cut to a predetermined size so that it is usedfor an optical recording card.

As shown in FIG. 4, an optical recording card 11 is so constructed thata front board 12 and a first intermediate layer 13 are adhered to oneanother with the use of an adhesive 14 with the optical recording medium1 interposed therebetween. A transparent polycarbonate having athickness of about 400 microns can be used for the front board 12.Similarly, a transparent polycarbonate having a thickness of about 50microns can be used for the first intermediate layer 13.

An UV setting type adhesive can be used for the adhesive 14, whilehaving a thickness of about 20 microns. A second intermediate layer 15is adhered to the bottom surface of the first intermediate layerb 13 asviewed in the drawing with the use of an adhesive 16. Necessary printedparts 17 are provided on the adhesive 16 using an UV setting type ink,while necessary printed parts 18 are similarly provided on the secondintermediate layer 15 using an UV setting type ink.

The second intermediate layer 15 is constituted by polycarbonate havinga thickness of about 200 microns and a thermoplastic adhesive can beused for the adhesive 16 by a thickness of about 20 microns.

A rear board 21 is adhered to the bottom surface of the secondintermediate layer 15 as viewed in the drawing using an adhesive 22.Polycarbonate having a thickness of about 50 microns can be used for therear board, while thermoplastic adhesive can be used by a thickness ofabout 20 microns for the adhesive 22.

A method of producing an optical recording card as described above iscarried out in the following manner.

First, as shown in FIG. 5, the optical recording medium 1 is temporalilysecured to a front board 12. Next, an UV setting type adhesive 14 iscoated on a first intermediate layer 13. Next, the front board 12 issuperposed on the first intermediate layer 13 and ultraviolet ray isradiated to the layered structure so that the front board 12 is adheredto the first intermediate layer 13. Next, an thermoplastic adhesive 16is coated on a second intermediate layer 15. Next, printed parts 17 and18 are placed on both the surfaces of the second intermediate layer 15using UV setting type ink. Next, a thermoplastic adhesive 22 is coatedon a rear board 21. Next, the layered structure of the front board 12and the first intermediate layer 13, the second intermediate layer 15and the rear board 21 are superposed one above another in a laminatedstructure whereby a required optical recording card 11 is built.

Advantageous Effect

In accordance with the above-described method of producing an opticalcard, the optical recording medium 1 is handled in such a manner that itis clamped between the front board 12 and the first intermediate layer13. Thus, there is no fear that the optical recording medium 1 isdeteriorated or degraded during production of the optical recordingcard. Consequently, an optical recording card including recordedportions having a high degree of cleanliess can be obtained. Further, ifa layered structure comprising a front board, an optical recordingmedium and a first intermediate layer which are superposed one aboveanother is previously provided, a various kinds of optical recordingcards can be produced merely by preparing a second intermediate layer onwhich necessary printing is effected in dependence on a required kind ofproduct and adhering it to the aforesaid layered structure later. Inview of the fact as mentioned above, it is possible to carry outproduction in small lot, resulting in the optical recording card beingproduced at an inexpensive cost.

What is claimed is:
 1. A method of producing an optical recording mediumin which an intensity of reading light is below a recording threshold ofthe medium and in a range of 1/5 to 1/10 of that of recording light,said recording medium consisting essentially of a layer of coloringmatter superposed on a photosensitive member,wherein said methodcomprises the steps of forming a photosensitive member comprising aphotographic emulsion layer containing silver halide grains, saidphotographic emulsion layer being located on a base board, blackeningsaid photosensitive member to release silver grains by exposing saidphotosensitive member to light, silver halide grains of saidphotosensitive member being suspended in said emulsion, developing andfixing said photosensitive member, and forming a coloring matter layerconstituted by dyestuff only which has a thickness in the range of 50 to2000 angstroms and has an ability of absorbing near-infrared radiation,said coloring matter layer being located on the photographic emulsionlayer.
 2. A method of producing an optical recording card in which anintensity of reading light is below a recording threshold of the mediumand in a range of 1/5 to 1/10 of that of recording light,wherein saidmethod comprises the steps of temporarily adhering to a transparent cardfront board an optical recording medium including a photographicemulsion layer containing a suspension of fine silver halide grains insaid emulsion and a coloring matter layer constituted by dyestuff only,said coloring matter layer having a thickness in the range of 50 to 2000angstroms and having an ability of absorbing near-infrared radiation,said adhering step placing said photographic emulsion layer and saidcoloring matter layer on a base board to build a layered structure insuch a manner that said coloring matter layer faces said card frontboard, adhering a first intermediate layer to the coloring matter layerside of said card front board, adhering a second intermediate layer tosaid first intermediate layer and then adhering a card rear board tosaid second intermediate layer.
 3. An optical recording card in which anintensity of reading light is below a recording threshold of the mediumand in a range of 1/5 to 1/10 of that of recording light comprisingatransparent card front board, and an optical recording medium adhered tosaid card front board; a first intermediate layer adhered to saidoptical recording medium, a second intermediate layer adhered to saidfirst intermediate layer, and a card rear board adhered to said secondintermediate layer; wherein said card front board and said opticalrecording medium and said first intermediate layer and said secondintermediate layer and said card rear board are superposed one aboveanother to build a layered structure; said optical recording mediumcomprises a base board and a photographic emulsion layer which has athickness in a range of 0.1-10 microns and which includes a suspensionof fine silver halide grains in said emulsion, the photographic emulsionlayer being located on the base board; and said optical recording mediumfurther comprises a coloring matter layer constituted by dyestuff onlywhich has a thickness in the range of 50-2000 angstroms and has anability of absorbing near-infrared radiation, the coloring matter layerbeing located on the silver grain layer, the base board and thephotographic emulsion layer and the coloring matter layer beingsuperposed one above another to form a layered structure wherein saidcoloring matter layer faces said card front board.
 4. An opticalrecording medium in which an intensity of reading light is below arecording threshold of the medium and in a range of 1/5 to 1/10 of thatof recording light consisting essentially ofa base board, a photographicemulsion layer and a coloring matter layer; wherein said photographicemulsion layer comprises a suspension of fine silver halide grains, saidphotographic emulsion layer being located on the base board; thecoloring matter layer constituted by dyestuff only which has a thicknessin the range of 50 to 2000 angstroms and has an ability of absorbingnear-infrared radiation, the coloring matter layer being located on saidphotographic emulsion layer; said photographic emulsion layer and thecoloring matter layer are superposed one above another to build alayered structure, at least a part of the photographic emulsion layerbeing blackened by exposure to light followed by developing and fixing,wherein at least another part of the said photographic emulsion layer isblackened by exposure to light to build an optical recording portion;and said optical recording medium has a threshold level of light energydensity of at least 3 mW/5 μmφ for deformation of said optical recordingmedium.